Heat stable lithium-lead soap composition



United States Patent F HEAT STABLE LITHIUM-LEAD SOAP COIVIPOSITION Terence B. Jordan, Fishkill, N. Y., and Oney P. Puryear, Houston, Tex., assignors to The Texas Company, New. York, N. Y., a corporation of Delaware No Drawing. Application May 2, 1956 Serial No. 582,069

6 Claims. (Cl. 252-625) This invention relates to a heat stable fluid composition which has the ability to retain metals suspended therein. More particularly, this invention relates to a heat stable fluid designed for use as a carrier vehicle for iron in a magnetic clutch.

The heat stable fluid composition of this invention comprises a highly refined mineral lubricating oil having a V. I. of at least 80 as the major component, 2 to 4 weight percent lithium salt of a C to C hydroxy fatty acid and 0.5 to 2 weight percent of a lead salt of a C to C hydroxy fatty acid, the total salt concentration falling between 2 and 6 weight percent of the composition. The addition of iron particles to the heat stable composition of this invention produces an excellent mag netic clutch fluid.

The requirements of a fluid to be employed as the power transmitting means in a magnetic fluid clutch are the following: a high viscosity index, a high flash and fire point, low vapor pressure and high temperature stability. The National Bureau of Standards in their development of the magnetic fluid clutch discovered that a highly refined mineral lubricating oil filled these requirements and that a mixture comprising 1 part of a 10 grade paraffin base mineral oil and to 9 parts of finely divided iron, prepared by decomposing iron carbonyl, was a good power transmission fluid. It was soon discovered that iron particles tended to settle out of 10 grade mineral oil during idle periods and caked on the bottom of the housing wherein the magnetic fluid clutch was encased. As a consequence, considerable difiiculty in starting was encountered using a mixture of iron particles and 10 grade mineral oil as the power transmitting fluid.

Any material added to the mineral oil to correct its deficiencies in retaining the iron particles in suspended form should have the following properties: (1) It should possess a relatively high gelling temperature. (2) It .should be stable on cooling statically from temperatures above the melting point of the added material. (3) It should not increase the transmission of torque due to increased consistency or viscosity of the medium when the clutch is de-energized. In addition, the added material should not adversely affect the previously mentioned properties of high viscosity index, low vapor pressure, high temperature stability and high flash and fire points. The composition of thisinvention, comprising a mixture of lithium and lead hydroxy fatty acid soaps in a mineral oil, fills all of the above requirements as will be demonstrated hereafter. e

Hydroxy fatty acids containing 12 to24 carbon atoms can be used in the formulation of the lithium and lead salts employed' in the composition of this invention. 12- hydroxy stearic acid is usually employed as the lead'and lithium soap, precursor because of its availability and cost. Hereafter in the description of theinvention, 12- hydroxy stearic acid will be used win.-the production. of the lead and lithium soaps. Examples of other hydroxy acids that can be employed are the following; 9-

droxy stearic acid, S-hydroxy myristic acid and 10-hydroxy palmitic acid.

In order for the composition of this invention to be effective as a medium for maintaining iron particles in' suspension, the concentration of the lithium plus lead hydroxy stearates must fall between 2 and 6 weight percent. At soap concentrations below 2 weight percent, the mixture does not maintain the iron particles in suspended form. If the total concentration of lithium and lead hydroxy stearates is greater than 6 weight percent, the consistency of the fluid vehicle is too high with the result that the transmission of torque, particularly during start up, is adversely affected. The preferred concentration of the lithium plus lead soaps falls between 3 and 5 weight percent.

The lithium hydroxy stearate usually is present in an amount between 2 to 4 weight'percent of the vehicle composition While the lead hydroxy stearate constitutes 0.5 to 2 weight percent of the vehicle. The ratio of lithium hydroxy stearate to lead hydroxy stearate falls between 2 and 4. The preferred composition comprises the lithium and lead hydroxy stearates in a weight ratio of 3:1. A composition containing 3 weight percent lithium hydroxy stearate and 1 weight percent lead hydroxy stearate has proven extremely effective in an extended tillate lubricating oil fraction having a V. 1. above 80,

an SUS viscosity at F. above and a flash above 350 F. can be employed as the mineral lubricating, oil component of the fluid composition of this invention.

The composition of this invention can be prepared by' the addition of the prescribed amounts of lithium and lead hydroxy stearates thereto, but it 'has been found more convenient to form the lithium and lead soaps in situ by a process involving saponification of the hydroxy stearic acid by lead oxide and lithium hydroxide in the mineral lubricating oil base and subsequent dehydration of the saponified mixture.

A preferred procedure for forming the fluid composition of this invention is described in the copending application, Serial No. 582,068, filed of even date. In the copeuding application there is disclosed a process for obtaining improved yields of compositions, particularly greases, containing a mixture of lithium and lead hydroxy fatty acid soaps. The procedure for obtaining im-' proved yields of a soap-thickened composition containing a mixture of lithium and lead hydroxy fatty acid perature above 280 F. This procedure was employed 1n the formation of the compositions of this invention.

The effectiveness of various compositions for.v sus pending iron was determined in the laboratory by a procedure involving the addition of about 85% by weight of iron powder to the vehicle and evaluation of the mixture after a uniform mixture had been formed by ,s'tirring at room temperature. 50 ml. of uniform iron-vehicle mixture under test was heated to an elevated temperature with stirring, transferred to a ,50 all, graduate andal- Fatented Nov. 4, 1958 lowed to. stand. undisturbed for. an extended period. The

volume of separated oil was recorded at regular intervals and the amount of separation against time was determined for. each system; Powdered iron-mineraloil vehicles were usedas" atstandard; Theideterminations were made after one cycle of heating, after'I-Z' cycles of these compositions inrretaiuing finely. divided iron par-' ticles inlsuspension is shown vi'nl'the followingita'l-s'le in comparison withcompositions co-ntaining'other common suspending agents such as aluminum'steara'te, polyethylene' glycol oleate and'calcium naphthenate;

TABLE I Suspending power of stabilized mineral oil compositions for iron powder Ml; of Oil Separated from 50 ml.

of Composition Containing 85% Iron Powder 1 Cycle 12 Cycles- Iron Powder In:

Base Oil A 18 in 220 Hrs. 17 in 250 Hrs. Base'Oil'A containing 1.5% lith- 10 in 216 Hrsnn 8 in 64 Hrs.

ium 12-hydr0xy' stearate and 0.5% lead IZ-hydroxy stearatel. Base Oil A containing 3%.lith in 220Hrs; 0 in 250 Hrs.

ium lZ-hydroxy stearate and V 1% lead 12-hyd1'oxy stearate.

Base Oil A containing 12% 0211- 1 in 56 Hrs. 2 in 250 Hrs, cium naphthenate. V Base Oil B 161'n72 Hrs Base Oil B containing 3%.lith- 0 in 72 Hrs h ium 12-hydroxy stearate and 1% lead 12-hydr0xy stearate. Base OilB containing 2% polyin 72 Hrs.

ethylene glycol monooleate. Base Oil B containing 12% 021- 1.5 in 72 Hrsmn cium naphthenate.

Base Oil B containing 3% alumi- 11 in 72 Hrs num stearate;

a pour off? F. and aflash above 420 F. Base Oil B is a furfural refined,,solvent 'dewaiied, parafiin base distillate oilhaving SU S-viscosities at- 100 and. 210 F.

0f165 andYS O', respectively, a viscosity index of 100, a'

The datalin. the foregoingttable demonstrate that a composition..comprising- .a.refinedrdistillate oil and 2 to 5 weight .percent of a mixture of-lithium and lead 12- hydroxy; stearatesds. an excellent vehicle for maintaining finely divided iron. particles in suspension. The data show clearly that substantial improvement-of the base oil is obtained witha concentration'of 2' weight percent of lithium, andllead 12-li-ydroxy' steara-tes, but that much superior results areobtained when-jthe-total-soap concentrationfalls within the prefer-red concentration range of '3 'to 4.5 weight percent.

The calcium naphthenate-containingcomposition also showed good. efiectiveness in retaining ironfpa'rticles' in suspension. Although aluminum stearate' and polyethylene glycol cleate (glycol-having average molecular weight ,o'f'400) improved the ability oftheibase' oil to retain ir'onoparticlcs in suspension, neither was considered anietf'ective additive.

Since both calcium naphthenate andthemixture of lithium 1 and lead. 12-hydroxy stearates were-effective in" retaining ironpowder'in suspension, compositions con tainingnth'ese additives were scheduled for evaluation in a magnetic. fluid clutch. Before the compositionocom prising Base Oil A, 12% calcium naphthenate and iron powder could be evaluated, the iron particles separated from the oil with the result that it was not evaluated. However, the compositions comprising Base Oil A, 3% lithium 12-hydroxy stearat'e'; 1% lead 12-hydroxy stearate and iron-powder: was'runin ama'gnetic fluid clutch for 400 hours with outstanding results: The amount of iron powder, in each evaluation was approximately 7 parts by wcig It. A-lth'oughthe magnetic'clutch' was subjected to ircquent'sto'ps andstarts; nod'ifiiculty was encountered in start-up. There was no evidence of settling of iron particles in-the bottom .of. the housing encasingthe magnetic fluid clutch.

The composition of thisinvention comprising a highly refined distillate oil having 'a'V. I. above and an SUS viscosity at 100 F. above 150, 2 to 5 weight percent lithium hydroxy steara'teand 0.5 to 2 weightipercent lead hydroxy stearate; the total salt concentration falling}: between 2 and 5 weight percent,- is an outstanding vehicle 'I' for iron'powder. When magnetic fluid cluiches 'attainr greater commercial use, this fluid-vehicle in combination with- 5 to 9' parts by weight of finely dividediron, .is expected to be widely used.

Obviously, manymodifications and variations. of the; invention, ashereinbefore set forth, may be made with out departing from the spirit and scope thereof andyt therefore, only such limitations should be imposed as. are indicated in the appended claims;

We claim:

1. A heatstable composition consisting essentially of a liquid vehicle comprising a highly refinedminerallubria; eating oil having a V. I. of at least 80 as themajor component, 2 to 4 weight percent lithium salt ofhydroxy stearic acid, and 0.5 to 2 weight percent of the leadisait of hydroxy stearic acid, the total concentration ofsaid" lithium and lead salts being not more than 6 weight percent and not less than 2 weight percent and-finely" divided iron powder in' an amount between 5 and} parts by weight of said liquid vehicle.

2. A heat stable composition according to-claim 1 containing 3 weight percent lithium lZ-hydroxy stearatei and 1 weight percent lead 12-hydroxy stearate; V

3. A heat stable composition according to. claim 1' in which the weight ratio of said lithium 12-hydroxy stearate to lead; 12-hydroxy stearate falls between 2. and 4.

4. A heat stable composition according to claim: 1 1. in which said lubricating oil has an SUS viscosity; at F. above 150, and a flash above 350 F. V

5. A composition for'use as a magnetic clutch'fluid consisting essentially of a liquid vehicle comprising a;

highly-refined mineral lubricating oil having a V.- -l;.

ofat least 80, 2 to 4 weight percent lithium 12-hydroxyz stearate, 0.5 to 2 weight percent lead 12-hydroxy stearate,

the total concentration of said lithium and lead 12-. hydroxy stearates being not more than 6 weight percent weight of the liquid vehicle.

6. A composition for use as a magnetic clutch'fluid; consisting essentially of a liquid. vehicle comprisinganz SAE .10 grade parafiin base mineral oil having a viscosityl index above 80, 3 weight percent lithium l2-hydroxyx stearate, 1 weight percent lead 12-hy'droxy stearatc' and-1 finely divided iron powder in an amount betWeenLS and 9 parts by weight of saidliquid vehicle.

References Cited .inthe file of this "patent,

UNITED STATES PATENTS 1938' 

1. A HEAT STABLE COMPOSITION CONSISTING ESSENTIALLY OF A LIQUID VEHICLE COMPRISING A HIGHLY REFINED MENERAL LUBRICATING OIL HAVING A V. I. OF AT LEAST 80 AS THE MAJOR COMPONENT, 2 TO 4 WEIGHT PERCENT LITHIUM SALT OF HYDROXY STEARIC ACID, AND LEAD SALTS BEING NOT MORE THAN 6 WEIGHT OF HYDROXY STEARIC ACID, THE TOTAL CONCENTRATION OF SAID LITHIUM AND LEAD SALTS BEING NOT MORE THAN 6 WEIGHT PERCENT AND NOT LESS THAN 2 WEIGHT PERCENT AND FINELY DIVIDED IRON POWDER IN AN AMOUNT BETWEEN 5 AND 9 PARTS BY WEIGHT OF SAID LIQUID VEHICLE. 